The Commerce Department is acting very nervous about the investigation into the falsification of economic statistics.

Last Thursday, the House Oversight Committee, headed by Rep. Darrell Issa (R- Calif.), interviewed the first witness in its probe — a whistle-blower who alleges that Commerce’s Census Bureau did a lot of nasty stuff to the economic stats that most of the world holds so dear.

As the whistle-blower was being questioned in the Rayburn House Office Building, two guys from Commerce’s General Counsel office — very much uninvited — barged into the hearing.

An argument ensued, and the discussion had to be taken out into the hall. The two intruders — one of whom I believe is a liaison between Commerce and Congress — insisted they be allowed to sit in.

Republicans on the committee said no. A decision among the lawmakers could not be reached, and eventually it was left up to the witness. The witness allowed the intruders to stay.

Now, I ask you: Is Commerce behaving like an agency that has nothing to hide?

As I have reported, a whistle-blower approached me in November and complained that workers at the Census Bureau were turning in fake surveys about economic conditions in this country.

Among a lot of other duties, Census compiles the data used by the Labor Department in calculating the monthly unemployment rate. This source said a data collector — officially called an enumerator — from Census’ Philadelphia office had been caught in 2010 falsifying more than 100 interviews a month.

Other allegations were that this enumerator, Julius Buckmon, wasn’t the only one playing with the surveys and that — when caught — Buckmon said the orders to falsify data came from higher-ups.

And that those higher-ups, in turn, said in private conversations that they were being protected by people even further up the chain of command.

If Buckmon wasn’t the only Census worker in Philly asked to falsify data — and false data was being entered in other offices — the US unemployment rate could have been corrupted.

And someone seems to have been protecting Buckmon, because even though he admitted to what he did, Buckmon was never fired.

The supervisors who were fingered as ordering the falsifying of the data weren’t fired either — and that’s curious, because Commerce in 2010 caught two supervisors in its Brooklyn office falsifying data that went into the much less important 2010 census, and they were immediately canned.

The accusations didn’t end there.

There was also a pervasive feeling around the Philly office that someone wanted the jobless figures during 2012 presidential election year to behave.

So when two goons from Commerce’s General Counsel office barged into the hearing last week, they were already nervous about their organization’s possible malfeasance. Now they have to worry about what else will come out as others from Philly are interviewed over the next few weeks.

I hear that two more Census workers will be grilled this week. Then comes the good stuff: supervisors who will have to explain their alleged involvement in Buckmon’s actions.

Issa’s committee has already complained that Commerce is being less than cooperative. A source with Oversight told me a while back that the “Commerce Department and the Census Bureau have been surprisingly hostile and non-cooperative in their responses to basic requests for documents and interviews, considering their public posturing that there is ‘nothing to see’ here.”

Some documents and e-mails have now been turned over, I hear. But the bulk of the material related to Buckmon and other possible incidences of data falsification are still being withheld by Commerce’s General Counsel, aka “the goons who invade hearings.”

I also hear that Commerce’s General Counsel’s office offered to help the people being called before the Committee remember what they knew. Witness tampering? I’ll let you decide.

The whistle-blower declined the General Counsel office’s help, which is probably why the interview last week became goon-worthy.

Last week I also began my own document search when I requested under the Federal Freedom of Information Act (FOIA) all e-mails sent from July 2012 to December 2012 to Census staffers from three higher-ups in the Philly Census office.

Those higher-ups are Thomas Almerini, program coordinator in Philadelpha; Timothy Maddaloni, supervisory survey statistician, and Fernando Armstrong, regional director in Philly. All three will probably be questioned by the committee in the weeks to come.

I chose e-mails from those dates for obvious reasons. I’d like to know if anyone fiddled with, or thought about fiddling with, the unemployment numbers in the months before the 2012 election.

Remember, there had been a sense that someone wanted the jobless numbers to cooperate. And they did.

The jobless rate, you might remember, had a fortuitous drop right after President Obama performed poorly in his first presidential debate against Mitt Romney, who for a split second was considered a serious opponent.

If there’s nothing to hide, Commerce should be more than willing to turn the e-mails over to me and to Congress.